Virgin Orbit CEO Dan Hart and Cloud Constellation President Cliff Beek at the World Satellite Business Week in Paris, France sign an agreement for a dozen satellites.

Air-launch rocket builder Virgin Orbit took another step in making low-cost rockets a reality in a new deal with satellite developer Cloud Constellation.

The Virgin Galactic spinoff, which is owned by billionaire entrepreneur Richard Branson, on Tuesday signed an agreement to launch a dozen communications satellites for Cloud Constellation's SpaceBelt system. The rocket company expects to begin delivering on the contract with its LauncherOne system in 2019.

"These missions wouldn't have been possible even a few short years ago," Virgin Orbit CEO Dan Hart said in a statement at the World Satellite Business Week event in Paris.

The low-Earth orbit constellation will be the backbone of SpaceBelt, to create a space-based data storage network. The individual units, considered small by the commercial space industry, each weigh around 400 kilograms or more than 800 pounds.

Source: Virgin Orbit

The two-stage expendable rocket and a fully-reusable air-launch platform of the LauncherOne service.

"The LauncherOne system was literally designed for companies and missions like ours," Cloud Constellation President Cliff Beek said.

Virgin Orbit's LauncherOne system is still in development. The company is planning the rocket's first test flight for early next year, with the system's Boeing 747-400 launcher in its final stages of flight testing. Virgin Orbit intends the two-stage LauncherOne system for use as both an expendable or reusable air-launched platform.

Branson's rocket company has also signed launch contracts with OneWeb, NASA, Sky and Space Global, and Sitael.